Dishwashers generally include a macerator system having a rotating chopper blade adjacent to a filter screen to pulverize and break down relatively large food particles to a size that allows the particles to pass through the filter screen. This system is needed to prevent the food particles from clogging the relatively small spray arm jet holes in the wash system upstream of the pump, particularly in the event of a malfunction of the dishwasher's filtration system. For example, large food particles may enter into the pump inlet if the consumer has not fully and properly placed the manual filter assembly back into the unit after removal for cleaning or other maintenance, or because of improperly assembled or defective filter components.
The size of the holes in the filter screen and axial spacing between the filter screen and chopper blade are thus important considerations in the proper operation of the macerator system. The macerator blade must be maintained in extremely close proximity to the filter screen, typically within about 0.060 inch from the screen. This spacing can be difficult to maintain due to such variables as machine manufacturing tolerances, normal wear of machine components, fluctuating operational conditions, and so forth.
U.S. Pat. No. 6,454,872 describes a system having a dual component shaft configuration between the motor drive shaft and chopper blade. The chopper blade is rotationally fixed to the filter screen and is detachably coupled to the motor drive shaft with a spring-biased coupling designed to accommodate axial tolerances of the drive shaft. This proposed solution, however, is relatively complex and introduces an additional point of potential mechanical failure (the coupling) between the motor shaft and chopper blade.
Accordingly, it would be desirable to provide a dishwasher with an improved macerator system that maintains the critical spacing between the chopper blade and filter screen in an effective and mechanically simple means.